The present invention relates to a helical scan magnetic recording and reproducing apparatus and, more particularly, to a magnetic tape guiding and tape loading mechanism of such an apparatus, which is suitable to enable a reduction in the size of the magnetic recording and reproducing apparatus in area and thickness.
For a helical scan magnetic recording and reproducing apparatus (VTR) its compactness in area and thickness is highly desirable in view of the portability thereof when applied to a VTR combined with a video camera such as an 8 mm video camera. In a VTR, a tape drive mechanism may occupy a large space thereof; therefore, a reduction of such space contributes to a compactness of a VRT.
In order to minimize the size of a tape drive mechanism, in Japanese Kokai (P) 63-239646, to reduce the thickness of the tape drive mechanism, a head cylinder device is arranged such that a portion of a cylindrical drum of the head cylinder device is received in a space provided in a front portion of a tape cassette and covered by an internal flap for tape protection in accordance with industrial standards, with the flap being opened when the tape cassette is inserted. For a tape loading, a so-called M loading system is provided wherein a portion of a magnetic tape is supplied from a tape cassette in parallel between a point on a supply reel side and point on a winding reel side of the tape cassette and helically wound on the cylindrical drum over a predetermined angle and is usually used in a VHS type VTR to reduce the thickness of the tape mechanism.
In the above proposed construction, a level of a center of the tape in a width direction on height regulating guide rollers provided in a tape supplying area and in a tape return area in the vicinity of the cylindrical drum for supplying the tape in parallel from the space of the cassette, is equal to a level of a center of the tape within the cassette at a time when the loading operation of the tape is completed.
In the proposed conventional technique, a pair of slanted posts for helically winding the tape on the cylindrical drum must be respectively positioned in the vicinity of the tape supplying and return areas. Therefore, an inclination angle and orientation of the cylindrical drum with respect to a reference plane of the apparatus and the height of the rotational center of the magnetic head mounted on the cylindrical drum with respect to a reference plane including a center line of the magnetic tape within the tape cassette are restricted.
More particularly, presuming a coordinate system having an original point corresponding to a rotational center of the magnetic head an X-axis extending in parallel to a straight line passing through the original point and connecting centers of the supply and winding reels in the tape cassette and a Y-axis passing through the original point and orthogonal to the X-axis, the orientation of the cylindrical drum is substantially within a third quadrant of this coordinate system, that is, the cylindrical drum is slanted toward the supply reel, and the inclination angle thereof is about 11.degree. to 12.degree.. Further, the level of the rotational center of the magnetic head is lower than the level of the center line of the magnetic tape within the cassette by several millimeters.
With such a head-cylinder arrangement, the amount of the cylindrical drum to be received in the open space of the tape cassette is very limited.
Further, since the inclination angle of the cylindrical drum exceeds 10.degree., the thickness of this mechanism, which depends upon the position of a lower edge of the cylindrical drum, is increased.
That is, there is a limitation in a gap between the inserted tape cassette and the cylindrical drum and there is a limitation in the size of the space to be occupied by the cylindrical drum, preventing the tape drive mechanism from being minimized.
In order to solve this problem and to allow the size of the tape drive mechanism to be made as small as possible, Japanese Patent Application No. 288912/1989 proposes arranging a cylindrical drum in a reference plane orthogonal to a straight line connecting rotational centers of the supply and take-up reels within a cassette and inclined toward the cassette with a predetermined angle of 6.degree. to 8.degree. from a straight line orthogonal to a plane on which the cassette is mounted and to make a winding angle of the magnetic tape on the cylindrical drum symmetrical with respect to the reference plane.